Twilight: Blue light filter

4.6
414K reviews
10M+
Downloads
Editors' Choice
Content rating
Everyone
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About this app

Are you having trouble falling asleep? Are your kids hyperactive when playing with the tablet before bed time?
Are you using your smart phone or tablet in the late evening? Twilight may be a solution for you!

Recent research suggests that exposure to blue light before sleep may distort your natural (circadian) rhythm and cause inability to fall asleep.

The cause is the photoreceptor in your eyes, called Melanopsin. This receptor is sensitive to a narrow band of blue light in the 460-480nm range which may suppress Melatonin production - a hormone responsible for your healthy sleep-wake cycles.

In experimental scientific studies it has been shown an average person reading on a tablet or smart phone for a couple of hours before bed time may find their sleep delayed by about an hour. See references below..

The Twilight app makes your device screen adapt to the time of the day. It filters the flux of blue light emitted by your phone or tablet after sunset and protects your eyes with a soft and pleasant red filter. The filter intensity is smoothly adjusted to the sun cycle based on your local sunset and sunrise times.

You can also use Twilight on your Wear OS device.

Documentation
http://twilight.urbandroid.org/doc/

Get more from Twilight
1) Bed reading: Twilight is more pleasant on the eyes for night reading. Especially as it is able to lower the screen backlight far below the ability of the backligt controls on your screen

2) AMOLED screens: We have tested Twilight on an AMOLED screen for 5 years without any sign of depletion or over-burning. If properly configured Twilight causes less light emission (by enabling dimming) with more equal light distribution (dark areas of the screen such as the status bar get tinted). This may in fact increase your AMOLED screen life time.

Basics on circadian rhythm and the role of melatonin
http://en.wikipedia.org/wiki/Melatonin
http://en.wikipedia.org/wiki/Melanopsin
http://en.wikipedia.org/wiki/Circadian_rhythms
http://en.wikipedia.org/wiki/Circadian_rhythm_disorder

Permissions
- location - to find out your current sunset/surise times
- running apps - to stop Twilight in selected apps
- write settings - to set back-light
- network - access smartlight (Philips HUE) to shield you household light from blue

Accessibility Service

In order to filter also your notifications and lock screen the app may ask for enabling Twilight Accessibility Service. The app uses this service only to better filter your screen and does not collect any personal information. Please read more about this at https://twilight.urbandroid.org/is-twilights-accessibility-service-a-thread-to-my-privacy/

Automation (Tasker or other)
https://sites.google.com/site/twilight4android/automation

Related scientific research

Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans Derk-Jan Dijk, & Co 2012

Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans Joshua J. Gooley, Kyle Chamberlain, Kurt A. Smith & Co, 2011

Effect of Light on Human Circadian Physiology Jeanne F. Duffy, Charles A. Czeisler 2009

Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans Claude Gronfier, Kenneth P. Wright, & Co 2009

Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans Kenneth P. Wright, Claude Gronfier & Co 2009

The Impact of Sleep Timing and Bright Light Exposure on Attentional Impairment during Night Work Nayantara Santhi & Co 2008

Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina Farhan H. Zaidi & Co, 2007

High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light. Lockley SW & Co. 2003

Sensitivity of the human circadian pacemaker to nocturnal light: Jamie M Zeitzer, Derk-Jan..
Updated on
Dec 25, 2022

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region, and age. The developer provided this information and may update it over time.
No data shared with third parties
Learn more about how developers declare sharing
No data collected
Learn more about how developers declare collection
4.6
414K reviews
Ali Erdaty
January 2, 2023
It is difficult to turn the app off. If I force stop the app, it turns itself back on within minutes. Response to developer: I do not like the filter system. I don't want a filter that automatically turns the app on - I just want an on and off button that I control. The notification brings up a whole extra panel. It takes multiple touches to pause and resume the app, plus closing the panel that appears. It just isn't convenient to use.
14 people found this review helpful
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Urbandroid (Petr Nálevka)
January 4, 2023
Hello Ali, so using a Pause widget would not solve your need for an on/off button?
M. Torres
January 20, 2023
Great app, and great customer support who immediately recognized my issue with the floating icon. Thank you so much! App is fantastic at the free version, enhanced features for the pro version. I've noticed my eyes feel heavier earlier in the day. I'm sure it's because of the reduced blue lighting, but I'm unsure whether this is a normal biological reaction or if it's healthy/safe. I've even reduced blue light on my television and I feel sleepier earlier in the day.
1 person found this review helpful
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Urbandroid (Petr Nálevka)
January 20, 2023
Hello, if your system shows a floating icon for apps with Accessibility service, disable this feature in system settings → Accessibility → Downloaded apps → Twilight. For more details, please contact support@urbandroid.org. Thank you.
human person
December 1, 2022
This is a great light filter app. You can change the color, use a slider to adjust both screen brightness and warmth of color tone, you can set timers to coincide with alarms, sunset/sunrise, or turn on and off manually. The simple screen widget with a birght red play/pause button is very helpful in turning the filter off, since it can essentially make the screen almost totally black. I really like it. 1 star off because it runs continually in the background on the Android 13 update. (~13kb/hr)
13 people found this review helpful
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Urbandroid (Petr Nálevka)
December 1, 2022
Hello, apps with Accessibility service must run in the background continually. And because Accessibility service is the only way to filter the Notifications, it is a trade-off on newer Android versions. For more details, please contact support@urbandroid.org. Thank you.

What's new

-Fix for drop down selections
-Wear OS app back in store
-Material 3 components
-Themed icon
-Tasker is default OFF, enable in Settings -More